GOST 18835-73

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  ГОСТ 18835-73

GOST 18835−73 Metals. A method of measuring a plastic hardness

GOST 18835−73
Group B09

STATE STANDARD OF THE USSR

METALS

A method of measuring a plastic hardness

Metals. Method for determination of plastic hardness

Valid from 01.01.1974
before 01.01.1979*
_______________________________
* Expiration removed by Protocol No. 3−93
Interstate Soweto standardization,
Metrology and certification (ICS No. 5/6, 1993). -
Note the manufacturer’s database.

DEVELOPED by the Volgograd Polytechnic Institute
The rector of the Institute A. G. Hardin
Supervisor Drozd M. S.
Responsible Slavske Y. I.
INTRODUCED by the Ministry of higher and secondary special education of the RSFSR

Zam. Minister Lebedev A.

The draft all-Union scientific research Institute of standardization (VNIIS)

Acting Director of Gliches A. V.

APPROVED AND promulgated by the Decree of the State Committee of standards of Ministerial Council of the USSR dated may 28, 1973 N 1332

This standard applies to ferrous and nonferrous metals and alloys with hardness ranging from 80 to 800 ND and specifies a method for measuring a plastic hardness at a temperature of 20±10 °C.

The method is based on measuring a plastic hardness of metals by pressing them to a spherical indenter.

1. EQUIPMENT

1.1. For the test to be applied to a machine according to GOST 9030−64 or hardness of the type TS-2 with the fixture described in the recommended application.

1.2. The depth dimension of the footprint of the bead on the test surface and the surface of the control bar should be indicator depth gauge with a scale division of 0.001 mm.

1.3. Used to measure the hardness of the plastic balls or spherical terminals should meet the following requirements:

a) when testing plastic materials with a hardness up to and including DN 450 are used as the beads or lugs of heat treated steel with hardness not less than HV of 850;

b) when testing plastic materials with a hardness exceeding 450 ND, apply the beads or lugs of the alloy with hardness not less than HV 1200 or diamond;

C) the surface of the ball or spherical tip with a diameter of 2 mm or more should not be below 12-th class of purity according to GOST 2789−59* and have no defects that are visible with a magnifying glass with 5-fold magnification. Tips with a diameter less than 2 mm needs to be carefully polished, have no defects visible at 30 times magnification. Limit deviations of the diameter of the ball according to GOST 3722−60**.
_______________
* Valid GOST 2789−73;
** A GOST 3722−81. — Note the manufacturer’s database.

1.4. The choice of ball diameter or radius of curvature of the spherical tip and also loads and produced in accordance with the requirements of the table.

1.5. When measuring a plastic hardness is allowed to apply load and any size, subject to the following conditions:

a) and ;

b) gradual increase of the load to the desired value;

C) the maintenance of a constant applied loads and within 15;

d) the application of loads normal to the surface of the test object.

2. PREPARING FOR THE TEST

2.1. The surface of the test sample was processed in the form of a plane so that the edges of the print were sufficiently clear to measure its diameter with any precision.

The surface of the test sample should be free from scale and other foreign substances.

In preparing the surface of the test sample it is necessary to take measures to prevent a possible change in the hardness of the test specimen due to heating or cold working of the surface when machined.

2.2. The minimum thickness of the test sample (products, objects) should be at least 10 times the depth of the imprint.

2.3. With the use of special holders it is necessary to take measures to prevent the deflection of the specimen during hardness measurement.

The test sample should lie on the stand steadily, so it could not happen of its displacement during hardness measurement.

3. TESTING

3.1. When measuring a plastic hardness of metals steel (carbide) ball or spherical tip, the radius of curvature of which is equal to , is pressed into the surface of the test specimen (product) is sequentially supplied loads and operating in for some time. After removing each load measure corresponding to the depth of the prints on the surface of the test object.

Allowed to produce the indentation of the bulb (tip) the power of the imprint obtained with the load (see drawing).

3.2. Load and can be made in one and the same point (again), so at different points of the test surface of the sample.

3.3. The distance from the center of the print to the edge of the sample should be not less than , and the distance between the centers of two adjacent prints must be at least 1.5, where the diameter of the ball.

When measuring a plastic hardness on samples or parts with curved surface length and width of the prepared flat surface should equal at least 2.

Measurement must be taken so that the results were not distorted by the phenomenon of swelling of the edges of the sample.

3.4. The depth of the imprint is measured using mechanical (the type of indicator depth gauge) readout devices, the error should not exceed 2%.

Relative error of load and shall not exceed ±1%.

Limit deviations of the diameter of the ball or the radius of curvature of the spherical tip shall not exceed 1% .

3.5. Tests are considered invalid:

a) upon detection of residual shear at the top of the tip after measuring the hardness, the value of which exceeds 2% of the depth of the imprint, or other surface defect of distortion for a given radius of curvature of the spherical tip;

b) failure to comply with the terms of the choice of the depth of the prints and in the range of 0,01−0,08.

In these cases the tip needs to be replaced and the test repeated with the application of appropriate loads and .

4. CALCULATION OF RESULTS

4.1. The number of plastic hardness () is calculated by the formula

,

where and  — load, kgf;

 — ball diameter or twice the radius of curvature of the spherical top of the tip, mm;

and the depths of the imprints, measured after removing the load and , respectively, mm.

Note. The number of plastic hardness, calculated according to a specified formula depending on the size of the depth of the prints and when the diameter of the ball , given in the Appendix.

4.2. When renowned plastic hardness, the approximate depth of the print () in mm can be calculated according to the formula

.

App

Continued

Note. The difference between the depths of the prints is given to the ball =10 mm. To determine the table of hardness values when tested ball with a diameter that is different from the 10 mm difference in depth of the prints should be multiplied by . For example, in the test of ball =5 mm obtained in the experiment, the difference in depth should be multiplied by 2 and the number of plastic hardness, taking respectively the resulting value .

Common accurate method of converting numbers of plastic hardness hardness values in other scales do not exist. Therefore, you should avoid such transfers, except in special cases when owing to comparative tests, is a sound basis for translation.

APPLICATION (recommended).

ANNEX to GOST 18835−73
Recommended

To determine the hardness by means of available on the production of static hardness testers of the type TS-2 without reconstruction and alterations may be applied to the device shown in Fig.

Damn. General view of the apparatus for measurement of the depth of the imprint directly on the hardness tester of the type TS-2

General view of the apparatus for measurement of the depth of the imprint
directly on the hardness tester of the type TS-2

The device consists of a special sleeve 1fixed to the housing unit TS-2 special screws (for mounting use the threaded holes provided on the front wall of hardness tester TS-2), swivel bracket 2in which is secured the indicator 3 gages with a leg ending with a ball indenter, mounted in the holder 4. The holder with the indenter mounted on the stem of the indicator through the thread. The ring 5 is fixed to the rod of the loading unit of the device, TS-2 and the bottom rests on the clip of the indenter 4, which serves as the end of the leg of the indicator.

The principle of operation. On the object table of the device TSH-2 establish the test sample 6. The rotation of the flywheel device TSH-2 raise the sample to the contact plane with the indenter. Upon further ascent stage with the sample the indenter rests on his clip into the lower section of the ring 5. Continuing the ascent of the table, select an available stroke of the loading unit of the device TSH-2. The indicator stalk rises up a few millimeters and reports the preload reading device. Then set the dial indicator to the zero position (fail zero division of the scale under the arrow of the indicator). The device is ready for operation. Pressing the «start» button of the device, TS-2, produce a loading of the indenter, whereby the latter is embedded in the test surface. The indenter penetrate into the test surface is shifted along with connected with him the leg indicator on the depth of the imprint. In this case, after removal of the load from the indenter, the arrow indicating device of the indicator captures his scale the number of divisions corresponding to the restored depth of the resulting print. Then, increasing the load until the next required steps, re-choose the gap between the indenter and the obtained surface of the imprint, set the scale indicator to a new zero position and clicking on the «start» button, load the indenter new higher load. After removal of the load from the indenter, the arrow indicating device of the indicator captures his scale the number of divisions corresponding to the difference of the depths of the restored prints obtained with the double indentation. The value of this difference and taken for testing forces and tables of annexes to this standard find the hardness value .

Note. If necessary, the indentation of the indenter in the surface of the test sample different loads can be realized in two different nearby points on the surface of the sample and the magnitude of the difference of the obtained depths of the restored prints find the hardness value of the same tables of the Annex to this standard.


The electronic text of the document
prepared by JSC «Code» and checked by:
the official publication of the
M.: Publishing house of standards, 1973